A DC-DC converter as an electric power converter that has a transformer, a rectifier connected to a secondary coil of the transformer, a noise filtering element such as a capacitor, and a metal plate for mounting these components is known (refer to Japanese Patent Application Laid-Open Publication No. 9-182433, for example).
A switching circuit s connected to a primary coil of the transformer.
The electric power converter generates a pulse wave using the switching circuit, and transforms this pulse wave using the transformer.
Then, a secondary voltage of the transformer is rectified using the rectifier.
When the switching circuit is operated with high-frequency switching, noise currents are generated in the secondary coil.
The noise filtering element is provided in the electric power converter so that the noise currents do not get mixed with an output current.
That is, it is constituted that the noise currents that have occurred from the secondary coil and passed the rectifier are sent to the plate through the noise filtering element, and are further sent to other electronic components to have the noise currents returned to the secondary coil.
Thus, the noise currents that are getting mixed with the output current of the electric power converter are suppressed by returning the noise currents to a source.
However, since a path where the noise currents flow is long in the conventional electric power converter, radiation noise from the path is easily generated when the noise currents flow.
For this reason, there is a possibility that the radiation noise leaks outside the electric power converter, or the radiation noise acts on other electronic components in the electric power converter and newly generates other noise currents.
Therefore, the electric power converter that is more excellent in a performance (noise filtering property) of shielding the radiation noise and the noise currents is desired.